Method of degreasing skins



Patented: Aug. 30, 1927. 1

UNITED STATES PATENT OFFICE.

CHARLES A. BROWN, OF SALEM, AND GUSTAVUS J. ESSELEN, JR., 0]! SWAMPSCOTT,

MASSACHUSETTS, ASSIGNORS TO MANUFACTURING IMPROVEMENT CORPORA- TION, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

METHOD 0]? nEGnEAs N'e sxms.

No Drawing.

The presentinvention relates to the treat-.

cient pressure upon the skin to remove the,

grease. Ordinarily a direct pressure exerte l'iupon' a' series of superimposed skins is employed for mechanically expressing the grease, although the necessary pressure is sometimes applied through a wringing ac; tion. This method of removing the --greas may be preceded by a preparatory milling operation in which the skins are warmed and subjected to a mechanical agitation in a brine solution to soften the skins and otherwise facilitate grease.

.The grease thus expressed from within the body of the skin collectsft'o a greater or less extent upon the surface and must subsequently be removed through the use of an alkali or similar treatment. Furthermore, this method of removal frequently color or dye.

leaves non-uniform bodies of grease remaining within the skin, which seriously interfere with the subsequent operations, .more par-,

.ticularly in cases Where it is desirable to secure an even tann ng and penetration of in this manner may necessitate the exertion of a very substantial pressure and even with the use of suflicient pressures it has been found that certain skins cannot be satisfactorily degreased Without subjecting them to further treatment, which is'hot only expen-' sive and tedious but if not properly performed may injure the skin. This is due in part to the fact that'the employment of too high a pressure for the purpose of expelling the grease ruptures the skin and seriously impairs its value.

According to the presentmet'hod the skins aresubjected to treatment with an aqueous emulsion of a grease solvent insoluble in water which is designed to penetrate the skin and act upon the contained greases in a manner to soften the greases. Folldw- Application filed July 25,

the expelling of the The expression of the grease 1924. Serial No. 728,117.

ing this preparatorytreatment, the greases thus softened by the action of the emulsion may be readily expressed from the skins in a fluid or semi-fluid condition. This subsequent expression of the greases may be accomplished either through a pressing, wrlnging, or washing operation. In addition to facilitating the removal of the greases from the usual type of skins. the

method actually produces a quality of skin which is superior to that p'roducedby ex:

is'ting methods. to the fact that any small amounts'of: residual greases are caused to be distributed more or less uniformly throughout the body of the skin, thus promoting an even penetration of the tanning or dye liquor, or both. The general behavior of skin subjected to the-present method also indicates that the removal of the desiredquantity of grease is accomplished without substantially affecting the collagen content of the skin.

In the simplest and best form of the invention now known, the skins as received in bundles in pickle or brine'are immersed in an aqueous emulsion of a hydrocarbon grease solvent and milled or agitated to soften the skins and aid in the absorption of emulsion thereby. In actual practice, an

This is believed. tobe due emulsion consisting of fifty-eightvparts of a petroleum fraction having a flash point he tween 100 F. and 113 F. and s'ufliciently free from high boiling fractions to .avoid leaving objectionable odors in the skin, three parts of'a-neutral olive oil soap, and thirtyto permit the emulsion to properly penetrate the skins, which period may approximate twenty to thirty minutes, theymay be either directly removed to the usual form of hy- 'draulic press or first immersed in a warm brine solution at-90 to 100 Fahrenheit until subjected to the pressing operation. The best results are perhaps obtained by allowing the skins to stand in the air for approximately two hours .and thereafter immersing them in the warm brine solution. The treated skins are allowed to remain thus immersed in a brine solution for approximately one hour longer prior to the mechanical expression of the greases. In the pressing operation, the warm treated skins are subjected to substantial pressure, which may vary with the condition of the skin and the amount and character of the grease.contained therein from seventeen hundred pounds per square inch to. twenty-five or twenty-six hundred pounds per square inch approximately. In the usual operation of such presses, a considerable number of superimposed skins are subjected to pressure simultaneously. The pressingoperation results inthe expressionof the grease bearing emulsion in the form of a fluid or semifluid.v The expression of the contained grease in this manner results in the reclamation of a larger percentage of grease and leaves the skins in condition for the, subsequent tanning operation, without the necessity for re-washing to remove the remaining grease. As stated previously, the removal of-thegrease in this manner produces a leather which takes the usual finishes evenly without causing the leather to be spotted or blotched. The uniform distribution of any traces of residual grease which may be present also produces a softer and better leather than appears to be possible with existing processes.

Although' the present invention has proved highly successful and is apparently best adapted" r015 the degreasing of sheepskins, nevertheless it is to be understood that the field of the invention is not limited to the treatment of skins of this particular character but may well embrace the treatment of other animal skins which present a similar problem from the deg-reusing standpoint. It is furthermore to be understood that the terniinology skins as employed throughout the specification and claims includes not only skins in pickle, and tanned skins, from which the hair has been removed but also skins which have not been de-haired and which are commonly referred to in the trade as shearlings.

WVe claim 1. The method of degreasing sheep skins prior to tanning, which consists in uniformly penetrating the skins and dissolving the contained greases with an aqueous emulsion of an inflammable hydrocarbon grease solvent insoluble in water and sufiiciently free from high boiling fractions to avoid'leaving objectionable odors in the skins, and subsequently removing the liquid grease bearin solvent emulsion from the skins.

2. The method of degreasing sheep skins prior to tanning which consists in agitating the skins with an aqueous emulsion of an inflammable hydrocarbon grease solvent insoluble in water and sufliciently free from h1gh boiling fractions to avoid leaving obectionable odors in the skins to cause uniform penetration of the skins and dissolving of the contained greases by the solvent, immersing the skins in a brine solution at a temperature below the flash point of the solvent, and subsequently expelling the dissolved and softened greases from the skins. 3. The method of degreasing sheep skins prior to tanning which consists in agitating the skins with a dilute aqueous emulsion of a petroleum fraction having a flash point on the orderof 100 F. and sufficiently free from high boiling fractions to avoid lea"- ing objectionable odors in the skins, and subsequently removing the liquid grease bearing emulsion from the skins.

CHARLES A. BROWN. GUSTAVUS J. ESSELEN, J R. 

